In the popup window "Edit indexes" existing indexes are managed or new indexes can be added.
When a new index will be created, the only required field is the "key" field. All other inputs are optional and can be reached via the "Advanced settings" item. For more detailed informations about the settings for the indexes the info icons beside the field labels can be used. A detailed documentation can be found here: http://docs.mongodb.org/manual/core/indexes-introduction/
Geospital-indexes are currently not supported.